SN 1988Z is the most luminous X-ray-emitting supernova, initially detected in 1995 using the ROSAT HRI with a luminosity of ~8 × 1040 ergs s-1 (Fabian & Terlevich 1996). Its high luminosity was ascribed to expansion of the blast wave into an especially dense circumstellar medium. In this paper, we describe a recent observation of SN 1988Z using the ACIS detector on Chandra. We readily detect SN 1988Z, obtaining ~30 net counts, which corresponds to a 0.2-2.0 keV luminosity of ~3.2 × 1039 ergs s-1. The calculated quantiles for the extracted counts allow a broad range of temperatures but require a temperature hotter than 5 keV if there is no intrinsic absorption. The long-term light curve (1995-2005) declines as t-2.6±0.6. This is one of the steepest X-ray light curves. The X-ray luminosity indicates that the emitting region has a high density (10 5 cm-3) and that the density profile is not consistent with a constant mass-loss stellar wind during the ~5000 yr before the explosion. If the circumstellar medium is due to progenitor mass loss, then the mass-loss rate is extremely high (~10-3 M☉ yr-1 [vw/10 km s-1]). The X-ray results are compared with the predictions of models of SN 1988Z.
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